1. Field of the Invention
The present invention relates to a radiation image capturing apparatus including a radiation detector for detecting a radiation image of a subject as electrical charge information and generating an electrical signal representing the electrical charge information. More particularly, the present invention relates to a radiation image capturing apparatus capable of protecting the radiation detector from electromagnetic noise.
2. Description of the Related Art
In the medical field, radiation image capturing apparatus is extensively used, which exposes a subject (patient) to radiation and receives the radiation that has passed through the subject with a radiation detector to capture a radiation image. Examples of known radiation detectors that can be utilized in the radiation image capturing apparatuses include conventional radiation films that are exposed to record radiation images, and stimulable phosphor panels that store a radiation image into a phosphor in the form of radiation energy and allow the radiation image to be retrieved as stimulated light when exposed to stimulating light. In order to provide a visible radiation image, in the former case, the radiation film, on which radiation images are recorded, is developed using a development device. In the latter case, the stimulable phosphor panel is supplied to a reading apparatus to allow readout of the radiation image.
In environments such as operating rooms, however, rapid readout and display of the radiation image from the radiation detector after acquisition of the image are required to enable prompt and suitable treatment. To meet such requirements, radiation detectors employing solid-state elements have been developed. Such detectors convert radiation either directly into electrical signals or first into visible light with a scintillator and then into electrical signals.
Whichever of above-mentioned radiation detector types is used, only a small analog signal is generated. The small analog signal is generally amplified by an amplifier disposed in the vicinity of the radiation detector. If the analog signal includes noise, however, this noise is also amplified, and the S/N ratio of the signal drops. To address this problem, Japanese Laid-Open Patent Publication No. 2005-283262, for example, has proposed a measure to counter noise on the analog signal generated by the radiation detector.
The Japanese Laid-Open Patent Publication No. 2005-283262 discloses, as shown in FIG. 1 thereof, an image detector in which an amplifier circuit 8 is held between cushioning materials 16 and 17. The cushioning material 16 prevents propagation of mechanical vibration from a cooling system 15 to the amplifier circuit 8, while the cushioning material 17 prevents propagation of mechanical vibration from a substrate holder 4 to the amplifier circuit 8 (see paragraph 0032 and the like of the Japanese Laid-Open Patent Publication No. 2005-283262).
In addition to preventing the effect of mechanical noise such as mechanical vibration, it is also necessary to prevent electromagnetic noise from affecting the radiation detector. In Japanese Laid-Open Patent Publication No. 2005-283262, however, silicone thermal-conductive gel is used for the cushioning material 16, and silicone heat insulating material for the cushioning material 17 (see paragraph 0030 of the Japanese Laid-Open Patent Publication No. 2005-283262), and thus no consideration is given to electromagnetic noise. However, the presence of electromagnetic noise on the analog signal from the radiation detector causes degradation in the quality of the generated radiation image.